On 05/31/20 at 01:37am, Anatol Pomozov wrote:
Hi Andrew, thank you for the quick response
On Sat, May 30, 2020 at 9:31 PM Andrew Gregory <andrew.gregory.8@gmail.com> wrote:
On 05/30/20 at 07:51pm, Anatol Pomozov wrote:
Pacman has a 'key in keyring' verification step that makes sure the signatures have a valid keyid. Currently pacman parses embedded package signatures only.
Add a fallback to detached signatures. If embedded signature is missing then it tries to read corresponding *.sig file and get keyid from there.
Verification: debug: found cached pkg: /var/cache/pacman/pkg/glib-networking-2.64.3-1-x86_64.pkg.tar.zst debug: found detached signature /var/cache/pacman/pkg/glib-networking-2.64.3-1-x86_64.pkg.tar.zst.sig with size 310 debug: found signature key: A5E9288C4FA415FA debug: looking up key A5E9288C4FA415FA locally debug: key lookup success, key exists
Signed-off-by: Anatol Pomozov <anatol.pomozov@gmail.com> --- lib/libalpm/alpm.h | 10 ++++++++++ lib/libalpm/package.c | 31 +++++++++++++++++++++++++++++++ lib/libalpm/sync.c | 17 ++++++++--------- lib/libalpm/util.c | 35 +++++++++++++++++++++++++++++++++++ lib/libalpm/util.h | 1 + 5 files changed, 85 insertions(+), 9 deletions(-)
diff --git a/lib/libalpm/alpm.h b/lib/libalpm/alpm.h index c6a13273..9c5fff73 100644 --- a/lib/libalpm/alpm.h +++ b/lib/libalpm/alpm.h @@ -1403,6 +1403,16 @@ alpm_db_t *alpm_pkg_get_db(alpm_pkg_t *pkg); */ const char *alpm_pkg_get_base64_sig(alpm_pkg_t *pkg);
+/** Extracts package signature either from embedded package signature + * or if it is absent then reads data from detached signature file. + * @param pkg a pointer to package + * @param sig output parameter for signature data. Callee function allocates + * buffer needed for the signature data. Caller is responsible for + * freeing this buffer. + * @return size of a signature or negative number if error. + */ +int alpm_pkg_get_sig(alpm_pkg_t *pkg, unsigned char **sig); + /** Returns the method used to validate a package during install. * @param pkg a pointer to package * @return an enum member giving the validation method diff --git a/lib/libalpm/package.c b/lib/libalpm/package.c index 5c5fa073..e0e4d987 100644 --- a/lib/libalpm/package.c +++ b/lib/libalpm/package.c @@ -268,6 +268,37 @@ const char SYMEXPORT *alpm_pkg_get_base64_sig(alpm_pkg_t *pkg) return pkg->base64_sig; }
+int SYMEXPORT alpm_pkg_get_sig(alpm_pkg_t *pkg, unsigned char **sig)
This API is weird, why are you returning an int when neither of the successful values are int and can potentially overflow an int? You're returning the length of an allocated string, size_t is the appropriate type.
size_t is unsigned int. But this function returns positive length in case of successful signature read or negative value in case of error. Thus return value cannot be size_t.
I get that, but you chose that interface. Why? Surely it makes more sense to either return 0 on error, since you treat a missing sig as an error anyway, or take a size_t* arg like decode_signature.
+{ + ASSERT(pkg != NULL, return -1); + pkg->handle->pm_errno = ALPM_ERR_OK;
I don't like clearing pm_errno without a good reason. It generally doesn't serve any purpose and can get us into trouble if a function gets called during cleanup somewhere.
I personally do not feel that "pm_errno = ALPM_ERR_OK" is useful here and I am more than happy to remove it.
But I also I see this pattern is used a lot. Only this file (lib/libalpm/package.c) has like 20 use-cases of it. e.g.
off_t SYMEXPORT alpm_pkg_get_isize(alpm_pkg_t *pkg) { ASSERT(pkg != NULL, return -1); pkg->handle->pm_errno = ALPM_ERR_OK; return pkg->ops->get_isize(pkg); }
So I was trying to follow a standard practice here. Or are you trying to say that lib/libalpm/package.c examples I was looking at are incorrect?
I consider this an unfortunate anti-pattern. It has bitten us in the past by clearing pm_errno during cleanup just like I said. I haven't been motivated enough to go through and remove it so far, but I don't want to add any more instances of it.
+ if(pkg->base64_sig) { + size_t sig_len; + int ret = alpm_decode_signature(pkg->base64_sig, sig, &sig_len); + return ret == 0 ? (int)sig_len : -1; + } else { + char *pkgpath, *sigpath; + int len; + + pkgpath = _alpm_filecache_find(pkg->handle, pkg->filename); + if(!pkgpath) { + RET_ERR(pkg->handle, ALPM_ERR_PKG_NOT_FOUND, -1); + } + sigpath = _alpm_sigpath(pkg->handle, pkgpath); + if(!sigpath || _alpm_access(pkg->handle, NULL, sigpath, R_OK)) { + FREE(pkgpath); + FREE(sigpath); + RET_ERR(pkg->handle, ALPM_ERR_SIG_MISSING, -1); + } + len = _alpm_read_file(sigpath, sig);
You need to check for and handle failure.
Do you mean to handle a file read failure? But both successful and erroneous codepaths are the same - free() the resources and return "len".
What is pm_errno if read_file fails?
+ _alpm_log(pkg->handle, ALPM_LOG_DEBUG, "found detached signature %s with size %d\n", sigpath, len); + FREE(pkgpath); + FREE(sigpath); + return len; + } +} + const char SYMEXPORT *alpm_pkg_get_arch(alpm_pkg_t *pkg) { ASSERT(pkg != NULL, return NULL); diff --git a/lib/libalpm/sync.c b/lib/libalpm/sync.c index 8c01ad95..0ab0fe26 100644 --- a/lib/libalpm/sync.c +++ b/lib/libalpm/sync.c @@ -880,18 +880,17 @@ static int check_keyring(alpm_handle_t *handle) }
level = alpm_db_get_siglevel(alpm_pkg_get_db(pkg)); - if((level & ALPM_SIG_PACKAGE) && pkg->base64_sig) { - unsigned char *decoded_sigdata = NULL; - size_t data_len; - int decode_ret = alpm_decode_signature(pkg->base64_sig, - &decoded_sigdata, &data_len); - if(decode_ret == 0) { + if((level & ALPM_SIG_PACKAGE)) { + unsigned char *signature = NULL; + int sig_len = alpm_pkg_get_sig(pkg, &signature); + if(sig_len > 0) { alpm_list_t *keys = NULL; - if(alpm_extract_keyid(handle, pkg->name, decoded_sigdata, - data_len, &keys) == 0) { + if(alpm_extract_keyid(handle, pkg->name, signature, + sig_len, &keys) == 0) { alpm_list_t *k; for(k = keys; k; k = k->next) { char *key = k->data; + _alpm_log(handle, ALPM_LOG_DEBUG, "found signature key: %s\n", key); if(!alpm_list_find(errors, key, key_cmp) && _alpm_key_in_keychain(handle, key) == 0) { keyinfo = malloc(sizeof(struct keyinfo_t)); @@ -905,8 +904,8 @@ static int check_keyring(alpm_handle_t *handle) } FREELIST(keys); } - free(decoded_sigdata); } + free(signature); } }
diff --git a/lib/libalpm/util.c b/lib/libalpm/util.c index 76728eb4..3d57817b 100644 --- a/lib/libalpm/util.c +++ b/lib/libalpm/util.c @@ -1489,3 +1489,38 @@ void _alpm_alloc_fail(size_t size) { fprintf(stderr, "alloc failure: could not allocate %zu bytes\n", size); } + +/** This functions reads file content. + * + * Memory buffer is allocated by the callee function. It is responsibility + * of the caller to free the buffer + * + * @param filepath filepath to read + * @param data pointer to output buffer + * @return size of the data read or negative number in case of error + */ +int _alpm_read_file(const char *filepath, unsigned char **data)
Same as above.
+{ + struct stat st; + FILE *fp; + + if((fp = fopen(filepath, "rb")) == NULL) { + return -1; + } + + if(fstat(fileno(fp), &st) != 0) { + fclose(fp); + return -1; + } + + MALLOC(*data, st.st_size, fclose(fp); return -1); + + if(fread(*data, st.st_size, 1, fp) != 1) { + FREE(*data); + fclose(fp); + return -1; + } + + fclose(fp); + return st.st_size; +} diff --git a/lib/libalpm/util.h b/lib/libalpm/util.h index 4fc6e718..50a94489 100644 --- a/lib/libalpm/util.h +++ b/lib/libalpm/util.h @@ -155,6 +155,7 @@ int _alpm_fnmatch_patterns(alpm_list_t *patterns, const char *string); int _alpm_fnmatch(const void *pattern, const void *string); void *_alpm_realloc(void **data, size_t *current, const size_t required); void *_alpm_greedy_grow(void **data, size_t *current, const size_t required); +int _alpm_read_file(const char *filepath, unsigned char **data);
#ifndef HAVE_STRSEP char *strsep(char **, const char *); -- 2.26.2
-- apg